Power supplies for computer systems are often designed and developed for the power requirements of the computer system. In addition the local power capabilities are also taken into consideration. For example, for a larger system the computer may need to operate at 115 volts at 60 hertz and have a supply of 20 amperes (amps). However, most power outlets in homes in the United States and Canada provide 115 volts at 15 amps. If the system were to try to draw 20 amps, a fuse may blow or a circuit breaker may trip.
In addition European countries, Asian countries and others have varying power capabilities. For example, in Europe it is common to have an outlet supply 220 voltage power at 50 Hertz. It is common for power supplies to be developed so they are capable of sensing the voltage and frequency of the power supplied by the outlet and adjust accordingly. It is not a simple matter to sense the available current for a system for the power supply based on the provided power. If the amperage available to the power supply is not known, the power requirements must be developed for a worst case scenario. For example, if the amperage available is not known, the power supply may be limited to 15 amps. As an alternative the power requirements for the power supply may need to be specified, potentially limiting the application of the system. For example a power supply that requires 20 amps, may not be used in locations that only have 15 amp power outlets without the danger of fire, blown fuses or tripped circuit breakers.